In the manufacture of flip-chip devices, integrated circuits with active surfaces are often positioned with die bonding machines. Die bonders have settings that allow control of the depth of the die placement head. If the machine is not calibrated properly, the machine could push the device too hard onto the mating surface. This could crush or otherwise damage active surface devices as well as solid state electrical devices.
Further, in capacitive sensitive devices, if the die is not level, i.e. one side of the device is closer than another, or the gap spacing between the die and the substrate is not otherwise conforming, capacitive effects between the die and the substrate may cause deviation in the performance of the device from its modeled operation.
Precise tolerances are of particular importance in microwave devices, RF MEMS, or other capacitive loaded devices, such as for example cantilever accelerometers (where precise and parallel spacing of the cantilever from the substrate allows more effective voltage measurements). Moreover, the further away that the device is from the substrate, the greater the capacitance, and thus, the greater the loss factor. If the tolerances were more precise and the capacitive loading more uniform, the loss factor could be reduced. Further, more precise modeling of the capacitive effects could be obtained to improve performance.
Die bonding machines, however, have limited tolerances within which they can mate chips. Attaining precision micron and submicron dimensions placement is not readily obtainable with die bonding machines.
The smaller dimensions (micron and submicron), however, are becoming an every day requirement in the high speed semiconductor manufacturing process. One technique to provide these smaller dimensions is a photolithograph process of etching physical stops on the integrated circuit itself. Although physical stops can be etched to provide submicron tolerances, such a process can increase the time and costs associated with chip processing.
Solder plated metal spheres and/or solder plated plastic spheres can be employed to provide gap control where larger gap spacing is acceptable, such as between an integrated circuit package and a printed wire board. Conventional solder plated metal spheres and solder plated plastic spheres, however, do not easily provide gap control in the micron and submicron range. Additionally, the manufacture of solder plated spheres can be a costly process.